Elemental devices used in integrated circuits can suffer significant variations in performance as a result of manufacturing conditions, manufacturing processes, operating conditions (both alternating current and direct current operating conditions), and ambient temperatures. In some instances, the basic parameters of a transistor device can suffer from variations of up to ±25% of a nominal value as result of variation due to processing, device aging, or operation outside of design specifications. These variations in performance can make an optimized integrated circuit difficult to design or operate, and may require over-engineering to ensure that operational requirements are maintained.
In particular, variations in manufacturing conditions, operating conditions, and ambient temperatures, can significantly affect a current gain (also referred to as “beta”) of one or more bipolar transistor devices within an amplifier, such as a radio-frequency power amplifier. Such variations can cause the current gain values to differ between each transistor device, and in some instances, change over time for a single transistor device. As most radio-frequency power amplifiers are sensitive to the current gain of included transistor devices, fluctuations can have a significant impact on amplifier performance, and can make optimal frequency performance difficult to achieve. For example, within a radio-frequency power amplifier, variations in the current gain can cause an adverse effect in the radio-frequency performance of the transistor devices, and can cause an operating point of the transistor device(s) to shift, both of which are undesirable.